<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 天花板，向上舍入整数
        // console.log( Math.ceil(25.5));//26
        // console.log( Math.ceil(-25.5));//25
    //    地板，向下舍入整数
        // console.log( Math.floor(25.5));//25
        // console.log( Math.floor(-25.5));//-26
        
        // console.log( Math.round(25.5));//26
        // console.log( Math.round(25.4));//25
        // console.log( Math.round(-25.5));//-25
        // console.log( Math.round(-25.4));//-25
        // console.log( Math.round(-25.6));//-26
        // console.log(Math.random());


        

        let stus = ['杨小凡','马超','冯元','罗文艺1','李2','雷悦']

        
        
        

        alert("中奖："+stus[-1])
    </script>
</body>
</html>